mmc: Add Extended CSD register to debugfs

Extended CSD is a MMC card register.  As increasingly interesting
fields are being added to Extended CSD, it is helpful to see its
value.  Note that SD cards do not have an Extended CSD
register, so it is MMC only.
Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/core/debugfs.c

@@ -184,6 +184,68 @@ static int mmc_dbg_card_status_get(void *data, u64 *val)
 DEFINE_SIMPLE_ATTRIBUTE(mmc_dbg_card_status_fops, mmc_dbg_card_status_get,
 		NULL, "%08llx\n");
 
+#define EXT_CSD_STR_LEN 1025
+
+static int mmc_ext_csd_open(struct inode *inode, struct file *filp)
+{
+	struct mmc_card *card = inode->i_private;
+	char *buf;
+	ssize_t n = 0;
+	u8 *ext_csd;
+	int err, i;
+
+	buf = kmalloc(EXT_CSD_STR_LEN + 1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ext_csd = kmalloc(512, GFP_KERNEL);
+	if (!ext_csd) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	mmc_claim_host(card->host);
+	err = mmc_send_ext_csd(card, ext_csd);
+	mmc_release_host(card->host);
+	if (err)
+		goto out_free;
+
+	for (i = 511; i >= 0; i--)
+		n += sprintf(buf + n, "%02x", ext_csd[i]);
+	n += sprintf(buf + n, "\n");
+	BUG_ON(n != EXT_CSD_STR_LEN);
+
+	filp->private_data = buf;
+	kfree(ext_csd);
+	return 0;
+
+out_free:
+	kfree(buf);
+	kfree(ext_csd);
+	return err;
+}
+
+static ssize_t mmc_ext_csd_read(struct file *filp, char __user *ubuf,
+				size_t cnt, loff_t *ppos)
+{
+	char *buf = filp->private_data;
+
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+				       buf, EXT_CSD_STR_LEN);
+}
+
+static int mmc_ext_csd_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+
+static struct file_operations mmc_dbg_ext_csd_fops = {
+	.open		= mmc_ext_csd_open,
+	.read		= mmc_ext_csd_read,
+	.release	= mmc_ext_csd_release,
+};
+
 void mmc_add_card_debugfs(struct mmc_card *card)
 {
 	struct mmc_host	*host = card->host;
@@ -211,6 +273,11 @@ void mmc_add_card_debugfs(struct mmc_card *card)
 					&mmc_dbg_card_status_fops))
 			goto err;
 
+	if (mmc_card_mmc(card))
+		if (!debugfs_create_file("ext_csd", S_IRUSR, root, card,
+					&mmc_dbg_ext_csd_fops))
+			goto err;
+
 	return;
 
 err: